When I cast balls (or bullets) I cast until I run out of lead, or time. I have never weighed balls...and I know I should. But I do weigh bullets. The process would be the same for balls: weigh a ball, and put it into a tuna tin or yoghurt container with a tag indicating the weight of the ball. Weigh another, and if it's within 1 gr. it goes into the same tin. If it is more than a grain either way, it goes into it's own separate tin. When you have weighed every ball, you'll find that you might have three tins, or four. But most of the balls will be in the middle tin, light balls to the left, and heavy to the right. When you go out to shoot, take only balls from one tin, or the other, but not both. It isn't the weight, per se, that is important, but the consistency. As my bro would say, "Consistency - thou art a jewel".